Friday, December 31, 2010

Update at 5:20 PM CST: "Significant" damage has been reported near Byram, MS. Additional damage reports are likely from the Richland/Pearl areas and southeast Jackson. Extremely impressive rotation noted on the radar about 4 minutes ago just North of Pearl:

See my original post below for additional information and how to interpret the wind motion (velocity) imagery as provided by the radar....

The above radar image was taken from the Jackson, MS radar at 4:59 PM CST. The left side of the image shows the radar reflectivity data (i.e., rain, hail, etc.) while the right side of the image shows the wind motion toward and away from the radar (click to enlarge).

On the wind motion image, the reds and oranges show wind blowing away from the radar (which is located near the upper right portion of the image - where the big black blank space is with the "KDGX" in light blue) while the greens and blues show wind blowing toward the radar. See where the reds/oranges and greens/blues meet in a tight spiral near Byram? That's where the radar is indicating strong rotation and a possible tornado.

Just a few minutes earlier, an actual on-ground tornado report was received North of Terry on I-55.

Residents of the greater Jackson area, particularly Richland, Pearl and southeast Jackson should prepare for a possible tornado as this storm races Northeast at 45 mph.

An unusual New Year's Eve severe weather outbreak continues to unfold at late afternoon. So far today, there have been over 20 tornadoes reported from extreme east-central Oklahoma, through Arkansas, Missouri and Illinois (click image above to enlarge).

The SPC currently has Tornado Watches in effect for the following areas:

The St. Louis Metro area (especially the southern half) has been particularly hard hit, with numerous reports of damage and injuries. Click on the image below to enlarge the severe weather reports map for that region:

The focus for severe weather has shifted further South during the past couple of hours, with Mississippi under the gun at the moment. The radar image below was taken a few minutes ago from the Jackson, MS radar. The pinkish/purple warning outlines depict 3 tornado warnings that were in effect at the time:

The left half of the radar image shows reflectivity mode (i.e., rain, hail, etc.), while the right half shows the motion of the wind as it blows toward (greens and blues) and away (reds and oranges) from the radar site (which is located in the right center portion of each frame).

The threat of severe weather will continue, particularly across portions of the deep south, into the evening hours.

Monday, December 27, 2010

Take a look at these awesome visible satellite images taken a few minutes ago, showing the power-house low pressure system responsible for the storm of the last 24 hours (spiral area of low pressure off of the New England coast). It almost looks like a hurricane!

I didn't spend a lot of time looking into it yet, but so far, I was able to find a barometric pressure reading of 28.59 inches of mercury at Chatham, MA earlier this morning as the low passed off to the East of that location. Keep in mind that a "normal or average" barometric pressure reading is closer to the 29.90-30.10 range.

In my earlier post this morning I mentioned that the snowfall totals as then reported by the NWS in NYC would probably be updated because many of them were taken while snow was still falling. They've in fact recently updated that list, and here it is below (by the way, Brooklyn & Newark ended up with 24 inches, Central Park 20 inches, Manhattan 10 inches and JFK airport with 15.5 inches of snow):

The YouTube video below pretty well sums up what most of NYC looks like this morning, after 24 hours of snow, including blizzard conditions at times:

The snowfall totals have been impressive, with as many as 26 inches reported at Tuxedo Park, NY (in Orange County). In NYC itself, as many as 22 inches have been reported in the Bronx, while 13 inches and 10 inches fell at Central Park and JFK airport, respectively.

Below is a map from the NWS Snow Analysis Center, depicting satellite estimated snow depths across the region as of 7am EST this morning:

Compare the observed snow depth to the forecast snowfall amounts that I posted from the computer model yesterday morning, and you can see that the model didn't do a bad job estimating the snowfall potential of this storm system (please note the scale is much more precise on the computer model vs. the snow depth image):

Below is the full list of reports as provided by the NWS in NYC (including parts of Connecticut, New Jersey & New York states). Please note many of the reports were only through Midnight or 1am this morning, and snow was still falling at that time so the final, total amounts will likely be higher in some areas. For purposes of brevity, only amounts of 10 inches or more are included:

Sunday, December 26, 2010

Above are just a couple of photos recently posted on Twitter, showing the heavy snowfall taking place currently across the NYC metro area. If you'd like to see more, just go to Twitter and search for "NYC Snow" or something similar, and you'll be bombarded with real-time tweets of all the action.

Thunder and lightning have been reported during the past hour at JFK airport and Central Park. Snow is currently falling at a rate of 2-3 inches per hour across much of the metro area, just as we had predicted in posts earlier today.

Winds have also continued to strengthen as we had forecast, with current steady winds of 35-40 mph and gusts of 45-50 mph at JFK airport. The wind will continue to intensify as the evening unfolds, with near blizzard to blizzard conditions likely at times.

This continues to unfold into a major snowstorm/blizzard for the area, and all travel is highly discouraged. Stay inside, light the fire and enjoy the storm!

The latest radar image from the NYC area (Upton, NY) radar shows moderate to heavy snow bands increasing and move onshore into Long Island and the remainder of the NYC metro area. The latest observation at the JFK International Airport confirms what the radar is showing, with heavy snow and one-quarter mile visibility:

As you also probably noted on the latest observation (times are Eastern, by the way), the wind had increased to 23 mph with gusts to 32 mph. Unfortunately, the wind will only grow stronger as the afternoon and evening wears on. Steady winds of 30-40 mph with gusts of 50-60 mph will be possible at times later this afternoon into this evening across much of the region. This will result in blizzard conditions across much of the region.

If you live or have travel plans anywhere along the Jersey to NYC to Boston corridor, it would be best to stay indoors and table those plans until at least Tuesday.

Below is the latest reflectivity image from the New York City area doppler radar. It shows bands of moderate to heavy snow increasing offshore along Long Island and much of the Northeast corridor:

The National Weather Service has issued Winter Storm and/or Blizzard warnings across much of the region through tonight (noted by the pink and orange areas on the map below):

A strong area of low pressure is still in the organization stages off the coast of North Carolina and Virginia. This system is already quite strong but will grow even stronger as the afternoon & evening progress.

By early this evening, the low pressure area will begin lifting North/Northeastward closer to the Long Island corridor, and heavy snows will increase into much of New Jersey, Long Island and New York City. Increased snowfall rates (of 2-3 inches per hour in some cases) along with strong North-Northeast winds of 40-50 mph with gusts to 60 mph will create very dangerous, blizzard conditions across much of the region.

The latest computer forecast model guidance is predicting total snowfall amounts of 15-20 inches to be widespread across much of New Jersey, Long Island and New York City, on Northeast toward the Boston area, through Monday morning.

If the above forecasts verify (which certainly appears possible based on the current trends), then 15-17 inches of snow will have accumulated in the greater NYC area by 7am EST on Monday morning.

Many airlines have already cancelled flights or are delaying flights across the region. Be sure to check ahead if you have any travel plans. The best move, in my opinion, would be to sit tight and ride the storm out and then try to move about again on Tuesday or Wednesday, if you possibly can.

Friday, December 24, 2010

...that strange substance falling from the sky this morning is just rain. I know it's been 45 or more days in some cases since we've last seen it, so I can understand your concern.

The above radar image taken a moment ago from the New Braunfels, TX radarshows that the activity is not widespread at the moment, but that should change later today as a strong disturbance lifts across the region from the West (indicated by the red and black "blob" over central Texas on the upper left panel of the image below).

The above image is the GFS Model forecast for 6pm CST this evening and if it verifies, rain should be widespread across much of the central & eastern two-thirds of Texas by mid-afternoon, into this evening. (Before that time, rain will be sporadic and widely scattered). A few rumbles of thunder will even be possible this afternoon or evening as the main part of the disturbance moves overhead.

Below is the latest forecast of total rainfall from the HPC for today:

You can see that a fairly widespread area of 1 inch (plus) rains is forecast from portions of the middle Texas coast into the northcentral part of the state.

Santa and the reindeer may not view this type of weather as most desirable for sleigh operations this evening, however it is much needed rain indeed for a very dry part of the country.

Wednesday, December 22, 2010

Earlier in the week I posted about the potential for a Christmas Eve snow event across portions of the Midwest, Tennessee and Ohio Valley areas. That still appears on track according to the latest GFS Model forecast below:

The HPC is currently forecasting a moderate chance for snow of 4 inches or more across portions of Missouri on Christmas Eve:

This band of locally heavier snow will then spread East/Northeast into portions of the Ohio and Tennessee Valley later on Christmas Eve into Christmas Day. Folks with travel plans into this region should check local forecasts for later updates. We'll also post another, more generalized, update here tomorrow.

In addition, Christmas Eve will bring a chance for measurable rainfall to much of the Eastern two-thirds of Texas and much of Oklahoma. Many locations across this region have gone 30 days or more without rainfall. Here is the latest HPC forecast of rainfall potential for Christmas Eve:

Somehow I don't think that Santa and the reindeer will feel too bad about getting a little wet across this very dry region!

Tuesday, December 21, 2010

The above photo was taken by NASA and streamed live on their website featuring the total lunar eclipse earlier this morning. The timing of this event, on the same day as the beginning of astronomical winter (winter solstice), is relatively rare (it's been nearly 400 years since this coincidence last took place).

There are hundreds (if not thousands) of pictures of the eclipse being posted from all around North America on Twitter right now. Enter the search term "lunar" or "eclipse" and you'll be taken right to many of them.

Today also happens to be the shortest day of the year in North America. As an example, here at my home near Kyle, TX, the sun rose today at 7:24 a.m. CST and will set this evening at 5:37 p.m. CST, giving a total of 10 hours and 13 minutes of daylight. Contrast that with 1 month from today, when the sun will rise at 7:28 a.m. and set at 6:00 p.m. CST, giving a total of 10 hours and 32 minutes of daylight.

To view sunrise/sunset times for specific dates at your location, I suggest WolframAlpha.com. Simply enter "sunrise at CITY, ST" and press enter (it will display both sunrise and sunset times and hours of daylight for the current date by entering that simple command). If you want to see data for another specific date (past or future) simply enter the date following the City and state (i.e., "sunrise at Kyle, TX January 21, 2011").

Sunday, December 19, 2010

Sometimes our words come back to haunt us. Apparently, this hazard also includes the "global warming" crowd...

Take a look at this story from The Independent in the UK on March 20, 2000. The headline read: "Snowfalls are now just a thing of the past". The first sentence of the article read: "Britain's winter ends tomorrow with further indications of a striking environmental change: snow is starting to disappear from our lives. Sledges, snowmen, snowballs and the excitement of waking to find that the stuff has settled outside are all a rapidly diminishing part of Britain's culture, as warmer winters - which scientists are attributing to global climate change - produce not only fewer white Christmases, but fewer white Januaries and Februaries..."

Flash ahead to today, December 19, 2010, and take a look at these photos from London and the central UK over the last 24-36 hours:

A white Christmas appears quite likely for much of the Ohio Valley and portions of the Midwest, as a strong storm system is forecast to take shape and affect the region on Christmas Eve and Christmas Day.

Below are the latest surface forecast maps from the HPC, valid 6am CST on Christmas Eve:

...and the same time on Christmas Day:

The potential exists for locally heavy snows along and North of the surface low pressure track, from portions of Missouri and Illinois on Christmas Eve, into the Ohio and Tennessee Valley regions on Christmas Day.

If your holiday travel plans involve air travel out of Kansas City, St. Louis or Chicago on Christmas Eve, keep a close eye on the weather and check for the latest updates as the week goes on.

We'll continue to monitor the computer forecast model trends over the next few days and provide more detailed posts as the week progresses.

Friday, December 17, 2010

The above image from the Amarillo radar a moment ago shows fairly widespread coverage of light snow across much of the Texas panhandle region. The picture below was posted on twitter, out someone's backdoor near Amarillo, about 2 hours ago:

Visibilities are not being greatly reduced by the snowfall, but the latest surface map below does show a few stations with visibility down to around 1 mile:

Light, to at times moderate, snow can be expected to continue across the panhandle region this afternoon, with 2 to 3 inches of total accumulation possible in some areas. A Winter Weather Advisory is in effect across the region this afternoon:

Sunday, December 12, 2010

UPDATE Monday, 7:45 AM:The following video is streaming on YouTube, showing the roof collapse from inside the stadium early Sunday morning:

Below is the text of my original post from Sunday morning:The roof of the Metrodome (home of the Vikings) in Minneapolis has collapsed this morning, apparently the result of the weight of heavy snow bearing down on the structure.

Here is a photo of what the Metrodome usually looks like (date unknown):

And here is a photo of what it looked like this morning after the collapse:

Flattened, I guess you could say, like a pancake...

According to an article in Wikipedia, "the roof is made of two layers of Teflon coated fiberglass fabric, and is an air-supported structure supported by positive air pressure. It requires 250,000 ft³/min (120 m³/s) of air to keep it inflated. It is reputed to be the largest application of Teflon on Earth."

Here is a photo of what the inside of the teflon roof looks like when properly inflated:

The region has been hammered by heavy snow over the past 24 hours, with blizzard to near blizzard conditions at times. As of 7am CST this morning, 15.7 inches of snow had fallen at the Minneapolis/St. Paul airport. Here is the latest snow depth map as produced by the NWS Snow Project:

A detailed graph of the activity at Minneapolis shows the snow fell in a relatively short period of time, and with a heavy "water equivalent" (or water content of the snow, which makes it more dense and heavy).

Fortunately this occurred at a time when the stadium was empty (other than a few support personnel that thankfully were not injured). It may, however, add more fuel to the controversy over the use of what some view as "non-permanent" materials in sporting and other public structures. Some of you may recall the collapse of the Dallas Cowboys Training Facility in strong thunderstorm winds back in May of 2009.

That facility was made out of a similar material, also supported by forced air, and was no match for the strong downburst winds of a severe thunderstorm. Many in the meteorological community, particularly those involved with warning and protecting the public during severe weather events, came out in force after that event and called for further review of the use of this type of structure where large numbers of the public meet.

Yesterday the Vikings management postponed today's game to Monday, which does indicate an awareness on their part as to the magnitude of the severe winter weather conditions that had been affecting the region. Thank goodness that move was made, or other support personnel would have been inside the stadium preparing for today's game when the collapse took place.

UPDATE 9:30 AM: Perhaps I gave the NFL & Vikings management too much credit in the last paragraph of my post. According to this article from KSTP, the game was postponed because the Giants were stranded in Kansas City due to the snowstorm, not out of concern for conditions in Minneapolis itself...

Friday, December 10, 2010

The National Weather Service's long range forecast branch (also known as the Climate Prediction Center) has just released their initial outlook for the period December 17th-23rd, or roughly the 7 day period leading up to Christmas Day.

Here is what they are forecasting for temperatures:

...and precipitation:

...and here is an image depicting the "mean" (or average) upper level flow pattern that accompanies the above forecasts for the same time period:

You can roughly interpret the forecast flow/location of the jet stream in the above map by focusing on the bands of green lines that run from Northwest to Southeast across the country. The particular pattern shown above does not generally reflect significant movement of cold air and/or storminess across the nation as a whole.

This trend is reflected in the first two maps, the temperature and precipitation departures from normal (where "B" = Below Normal, "A" = Above Normal and "N" = Normal). As you can see, the forecast calls for normal to above normal temperatures across the majority of the nation, with only a small region of below normal temperatures forecast along portions of the East coast.

As far as precipitation is concerned, the forecast of normal to below normal rain chances across the majority of the nation also reflects the rather inactive jet stream pattern described above.

There currently aren't even any indications that a significant disturbance is "waiting in the wings" to impact the nation right after Christmas, if the above flow pattern forecast verifies. We're still obviously about 15 days away from the big day, so we have plenty of time to monitor the trends and post any updates, but right now it looks like pretty quiet travel weather for most of the nation during the immediate period leading up to Christmas.

Monday, December 6, 2010

The National Weather Service has introduced several cool new tools to analyse snowfall data this season. Unfortunately (for me) I'm not in an area that experiences snowfall. (If we have a few flurries in January they're calling out the sand trucks here in South Texas). But for those of you who do experience snow events, these tools may come in handy, or if nothing else may just be of interest to you.

You can go to the site by clicking on the "snowfall data" hyperlink in the first paragraph. Here are a few sample screenshots taken from the site this morning. First shows the current snow depth across the nation:

This next one shows the water equivalent of that snowfall:

There are numerous other fields/parameters that you can examine on the site, but the last one I'll show here is kind of interesting, which depicts the average temperature of the snowpack (this can be useful in helping to forecast both high and low temperatures in and near the region for many days after a snow event):

﻿If you want to get a detailed analysis of snow statistics at a particular site, you can also do that by accessing the "station information" located at the bottom of the main page. For example, the data below were pulled for Christiansburg, VA through 06:00 GMT this morning, 12/6/10 (click to enlarge):

There are many other graphic variables that can be examined for each site, and you can also enter specific site location identifiers, latitude/longitude, etc. to examine the data from a given area.

The above products are generated by the National Operational Hydrologic Remote Sensing Center (NOHRSC - thank goodness for that!), a division of the National Weather Service. The unit is based in Minneapolis, MN, where they know a thing or two about snowfall.

They use various combinations of ground truth reports (including examination by air) and high resolution satellite data to produce the products. You can learn more about the processes and technologies that are utilized here.

As we proceed through the winter season, I'll attempt to make some real time event posts utilizing some of the data so you can see how it can be applied in a given situation.